It’s been known for a while that our planet’s magnetic field is perpetually changing its direction and intensity.
The rate at which these changes are happening is extremely important and of great interest, especially as the planetary feature is one of our most important shields against cosmic radiation.
However, a recent analysis of the lava flows in eastern Scotland helped fill in some significant blanks in the planet’s magnetic field history, as it was on par with past research suggesting that the planet has a 200-million-year cycle, during which it experiences fluctuations in intensity.
The team also relied on the magnetic history they discovered buried in the geological record to re-check other measurements carried out over the past decades and to settle a history of the planet’s magnetic field dating back some extra 500 million years.
Louise Hawkins, a paleomagnetist from the University of Liverpool in the UK, said:
“Our findings, when considered alongside the existing datasets, support the existence of an approximately 200-million-year long cycle in the strength of the Earth’s magnetic field related to deep Earth processes,”
She also explained that as nearly all of the available evidence for processes within the planet’s interior is constantly affected by plate tectonics, the preservation of the signal for deep within the planet is exceptionally valuable as one of the very few constraints scientists have to deal with.
Paleomagnetic analysis techniques in both the thermal and microwave domains were carried out on rock samples taken from the ancient lava flows. The alignment of mineral crystals within the samples revealed the state of our planet’s magnetic field back when they formed.
It was discovered that, between 332 and 416 million years ago, a dip in the magnetic field occurred, matching up one to 120 million years ago.
Estimates suggest that, during the Mid-Palaeozoic Dipole low, the earlier period, Earth’s magnetic field was only 25% as strong as it is today.